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M4 tunnel work under way

Engineers were this week making temporary repairs to the fire-damaged Brynglas Tunnel on the M4 near Newport in south Wales.

Resurfacing and lighting focus

Work is being focused on resurfacing and lighting to make the tunnel operational. More substantial refurbishment is not being implemented now because the tunnel is due to undergo a major upgrade to comply with EU legislation by 2014.

“A major refurbishment is in the pipeline, so we will schedule any major repairs in for that,” a South Wales Trunk Road Agency (SWTRA) spokesman said.

The 368m long tunnel opened in 1967 and consists of two-lane bores in each direction. The fire, which broke out on a lorry on 26 July, caused a three-day closure of the westbound bore reducing the M4 to a single lane contra-flow in the eastbound bore − causing tailbacks across the region.

Temperatures are believed to have reached up to 1,000°C.


Intense: Temperatures are believed to have reached up to 1,000oC

Tunnel ‘structurally sound’

The lining to the rock bored tunnel consists of a lower half concrete panel and upper half of plastic fireproof material. The spokesman said there was no spalling of the concrete and that damage was limited to the plastic tunnel lining, which had become rippled.

Examinations of concrete core samples showed the tunnel was structurally sound.

The road surface was also damaged where the lorry burnt out. During the closure workers repaired the roadway by laying patches of 40mm deep bitumen. Full resurfacing has also been held back until the major refurbishment.

Eventual major upgrade

The damaged westbound bore was initially reopened during daylight hours only, closing at night to allow engineers to install temporary lighting to increase the speed restriction from 30mph to 40mph and allow traffic to run during the night.

SWTRA said the eventual upgrade would involve replacing the concrete and plastic lining, installing new lighting and electronic signage, as well as carrying out resurfacing.

Investigations into the cause of the fire are ongoing but a preliminary report by the Welsh Assembly Government was due to be released as NCE went to press, which was expected to include further details of medium-term remediation work required.

M4 relief road

Last month’s fire in the Brynglas Tunnel has reignited calls for the construction of an M4 relief road near the tunnel in south Wales to alleviate traffic.

Plans for a six-lane relief road were dropped in 2009 after a change of government and as construction costs ballooned from £350M to £1bn.

However, business group CBI Wales this week said that the M4 was the most important piece of infrastructure in Wales and a new six-lane road was vital.

The Welsh Assembly Government responded by saying it is “more than aware” of the strategic and economic importance of the M4 to Wales” and is developing plans for a new dual carriageway in the area.

CBI Wales dismissed this idea as a temporary measure.

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